Many electronic devices are so sensitive to contamination from the environment that it is necessary to enclose them within a hermetically sealed package, that is, a package through which substantially no air or contaminants can enter from the external environment under conditions of normal use. One example of an electronic device that requires hermetic sealing in this manner is an electronic device filter known as the surface acoustic wave (SAW) device, as described, for example, in the paper of B. M. Butler, "Surface Acoustic Wave Devices," Electronic Engineering, June 1980, pp. 37-44. This device normally comprises a pair of metalized leads on a quartz plate which are terminated by transducers. Another pair of metalized leads are terminated by transducers a short distance away. Electronic energy in one pair of leads is converted by the corresponding transducers to acoustic power, which travels along the surface of the quartz plate to the opposite transducers, which converts it back to electronic energy. As is known, this process of converting the electrical energy to acoustic energy and back again to electrical or electronic energy can be used to perform desirable filtering functions on the electrical energy.
Since the acoustic wave energy travels on the surface of the quartz plate, it is particularly important that such surface be kept free of contaminants that could reflect or otherwise interfere with propagating surface acoustic wave energy. For this reason, it is customary to hermetically seal each SAW filter device in a hermetically sealed "can" or package. The hermetically sealed package, typically comprising metal elements sealed by metal bonding techniques, constitutes by far the major portion of the cost of the finished device since the device itself, being constituted only of a quartz plate and deposited metal films, can be made very inexpensively.
There are numerous other examples in which the cost of the hermetic package greatly exceeds the cost of the electronic device being hermetically sealed. There has therefore been a long-felt need for a less expensive method for dependably hermetically sealing electronic devices from the external environment.